Aluminum alloys



Patented Oct. 31, 1933 PATENT OFFICE ALUMINUM ALLOYS Walter A. Dean andLouis W. Kempf, Cleveland, Ohio, assignors to Aluminum Company ofAmerica, Pittsburgh,

Pennsylvania Pa., a corporation of No Drawing. Original applicationSeptember 21,

1932, Serial No. 634,156. Divided and this application November 645,130

30, 1932. Serial No.

1 Claim. (Cl. -1)

The invention relates to aluminum base alloys containing magnesium andcobalt and to such alloys of this nature as have excellent properties atelevated temperatures.

This application is a division of our copending application Serial No.634,156.

We have discovered that aluminum base alloys, by which we mean alloyscontaining about per cent by weight or more of aluminum, containing 1 to15 per cent by weight of magnesium, are greatly improved in theirproperties at high temperatures if there is added to the alloys amountsof cobalt from about 0.2 to 3.5 per cent by weight. The alloys by reasonof these additions of cobalt are considerably hardened, particularly asregards their properties at elevated temperatures, i. e., in theneighborhood of 400 to 700 Fahrenheit, and this increased hardness iseffected without an appreciable decrease in elongation. Since increasedhardness, without substantial decrease in' elongation, is a propertygreatly desired at elevated temperatures, the addition of cobalt to thealuminum-magnesium alloys above mentioned increases their com mercialusefulness, particularly their use as structural material inreciprocating parts operating at high temperatures. The addition ofcobalt in the amounts named also increases the ease with which thealuminum base magnesium alloys are cast in permanent molds.

The aluminum base alloys containing about 1 to 6 per cent of magnesiumand about 0.2 to

1 per cent of cobalt are readily placed in a wrought condition, and whenalloys for working are desired, we have found it advantageous tomaintain the cobalt content between 0.2 to 1 per cent since greateramounts of cobalt increase the difflculties of working without producingadvantages which compensate therefor. The aluminum base alloyscontaining 2.0 to 15.0 per cent of magnesium are most advantageouslyused as casting alloys, and in such case amounts of cobalt from 0.2 to3.5 per cent will produce the advantageous results above noted.

In these alloys the addition of 0.05 to 0.4per cent of antimony orbismuth, or both of these metals in total amount not exceeding thatnamed, has a pronounced efiect in maintaining a high elongation in thealloys when they are. subjected to elevated temperatures. Either or bothof these metals added to the alloys in total 0 amount much greater thanabout 0.4 per cent by weight bring about a decrease in elongation whichis very disadvantageous when the alloys are to be used at elevatedtemperatures.

As an example of the alloys herein described 5 may be cited an aluminumalloy containing 6 per cent of magnesium and 1.0 per cent of cobalt.This alloy after being treated for 4 hours at 700 Fahrenheit wasmaintained at a temperature of 600 Fahrenheit for 10 days at the end 70of-which time, and when tested at that temperature, it had a tensilestrength of 15,700 pounds per square inch. and an elongation of 8.2 percent in 2 inches. A similar alloy not containing cobalt but similarlytreated and tested has 75 a tensile strength of about 15,300 and anelongation of about 5.5 per cent in 2 inches.

The aluminum used in the manufacture of the alloys may be of the highestpurity or it may contain amounts of usual impurities, and 30 the termaluminum as used herein and in the claims designates the aluminum ofcommerce.

It is an incidental property of our alloys that the presence of iron inamounts as high as 2 per cent by weight is not harmful to the high 35temperature properties of the alloys and, therefore, a wide choicebetween the various grades of commercial aluminum is possible.

We claim:

A metallic alloy characterized by high physi- 0 cal and tensileproperties at elevated temperatures and consisting of 1.0 to 15.0 percent by WALTER A. DEAN. LOUIS W. KEMPF.

